Ejector pumps of this kind have been known for some time (FR-A1-25 77 284) and are being used for both, to generate vacuum and to move materials, capable of flowing. With a known sequential multistage design, a high degree of efficiency can be obtained, especially with high vacuum. This one has the advantage, that the flow energy of the working fluid, which can either be in gaseous or liquid form, is being used until the flow velocity has dropped below a level, which no longer can be used with any constructive effort.
Multi stage ejector pumps basically have the problem, in that the package size increases super-proportionally with the number of stages. This fact among others is due to the fact, that the cross sectional area of the flow channel has to increase from one stage to the next, and this will tend to expand the height of such an ejector assembly with several stages, without actually being able to use all of the entire volume. One example of this is an ejector pump having a square shaped housing.
The goal of this invention is, to improve ejector pumps of the type previously mentioned, so that in spite of the necessary enlargements of the flow channel, package size and especially package height can be kept small.
This task will be solved with an ejector pump having multiple pump stages for suction or for moving materials or material mixtures which are capable of flowing with the help of a working fluid within one housing. This is further accomplished with the ejector pump having a flow channel being circular in shape and constructed for a radially outward directed flow.
The ejector pump, according to this invention, in spite of extreme compactness and efficiency, can be easily manufactured, especially from (mass) turned or assembled parts. It can be manufactured from almost any material, as for example from metal, plastic, glass, ceramic, etc.
The principle of using a circular shaped flow channel for an ejector pump is basically already know from DE-A1-34 20 652--but solely for single stage ejector pumps. With this single stage ejector pump, it was basically a matter of high precision in order to realize very specific angular relationships and lengths in the area of the nozzle, the mixing zone and the diffuser. This could be accomplished by fashioning all essential parts such as the nozzle, mixing zone and diffuser on one or both faces as solid blocks, which could be accomplished in single phase, using a CNC controlled lathe. It resulted in high precision and good repeatability in the manufacturing of a large number of pumps. One significant disadvantage of this well known ejector pump is the fact that it consist of only a single stage. Another significant disadvantage is the fact, that the suction chamber, through which the flow medium or flow medium mixture is advanced towards the circular shaped, radially outward directed flow channel, is fashioned as a groove increasing its cross-section towards the flow channel, whereby the charging of this circular shaped groove with the flow medium or flow medium mixture take place through several, connecting openings spread out over the circumference, all of which end in a common antechamber. This type of construction, and the corresponding manufacturing process of these well known ejector pumps, results in undesirable flow relationships, for the flow medium or flow medium mixture as it is entering the circular shaped flow channel. An additional disadvantage of this well known ejector pump relates to the fixation on the very specific surface contour to be used for the flow channel. This allows an optimal pump efficiency only when the viscosity of the working fluid and/or of the flow medium or flow medium mixture lies within narrowly defined parameters. Different pumps each time are required to solve differing flow requirements, especially when moving a flow medium or flow medium mixture. Further problems are encountered if the viscosity of the same deviates from the ideal conditions for which this ejector pump had been designed, or when employing other work fluids. At least the pumping block has to be changed on the face of which the nozzle, the mixing zone and the diffuser has been worn in.
In contrast to this ringlike constructed ejector pump known from DE-A1-34 20 652, the ejector pump of this invention, has a series of significant advantages. One advantage is the fact, that it is very easily possible to apply the circular geometry of the flow channel and all of its related advantages to multi stage ejector pumps. Another advantage is the fact, that the flow relationships, compared to the single stage ejector pump known from DE-A1-34 20 652, are significantly balanced out as the flow medium or flow medium mixture enters the flow channel. Another advantage is, that in spite of being multi staged, the ejector pump, according to this invention, is easy to manufacture, since it can be build from simple turned or assembled mass produced parts, whereby the individual ejector rings can be reworked or exchanged, if necessary, for optimizing the ejector pump in each case for the required purpose.
The basic philosophy, on which the present invention is based, is, that in the case of a multi stage ejector pump, the circular shaped flow channel for radially directed flow from the inside out, can also used be put to practical use in such a way, that the wall areas of the flow channel in the mixing zone and the diffuser of one of the pump stages are axially adjustable in relation to the other walls of the flow channel. In this way, the flow relationships in the flow channel can be adopted to particular flow requirements, even with such multi stage ejector pumps, which do not have a narrow passage between the suction chamber and the flow channel, as with DE-A1-34 20 652.
The working fluid, as far as the invention is concerned, can be in liquid or gaseous form, as well as the flow medium or flow medium mixture which is capable of flowing.
"Ejector rings," as far as the invention is concerned, are preferably components, independent from each other, which are placed into the pump housing, which, as will be shown later, can be accomplished in various ways. As long as the cross sectional reduction at the passage for the flow medium or flow medium mixture, capable of flowing, between the particular suction chamber and the flow channel is not exceedingly great, it may be possible to machine the ejector rings with the wall areas, which make up the suction chamber, as a single piece.
The basic outline of the ejector rings (viewed in axial direction) should preferably be circular in shape. The cross section of the ejector rings (also viewed in axial direction) can be varied to a large degree, based on the requirements of the application: for instance, it can be cylindrical or preferably, conical in shape (see design examples according to FIG. 1 to 4). The side walls, forming a part of the flow channel of the ejector ring, can be fashioned with many contours, especially viewed radially towards the outside (see design examples according to FIG. 5 to 9). The angle of inclination of the mixing zone especially, referenced to axial direction of the flow channel, can be varied. The ejector rings can also have a wavy surface, which effectively enlarges the suction passage, and whereby the flow relationships in the flow channel are controlled by local cross sectional changes (see design examples according to FIG. 5 and 9). It is further advantageous to place flow directing profiles sideways, as seen in axial direction above the ejector rings, (see design examples according to FIG. 9), which makes it possible to reduce turbulence to a relatively low level, which may result by mixing of the flow medium or flow medium mixture with the working fluid. The guiding profiles make it further possible to reduce the residual energy of the working fluid, which in turn increases the efficiency factor of the pump. Such flow channel designs have not been made public.
The mounting of the ejector rings can be basically done on the faces of the divider wall, separating the two suction chambers, but it is especially of advantage if they are already attached to the divider walls before assembly, and preferably are in one piece, so that the subassembly, consisting of ejector ring and divider wall, can be installed into the pump.
While the position of the individual ejector rings (as viewed in axial direction) in relation to each other as well as to the remaining parts of the pump can remain unchanged in most cases, one special feature of the invention is, that the axial position of the ejector rings, and consequently the cross sectional shape of the flow channel can be changed. Such a change in position can be accomplished in several different ways, as for example with the use of slides or screw threads, the diameter of which can correspond to the diameter of the corresponding ejector ring. Especially easy to manufacture, to assemble and to adjust afterwards from the outside are such adjustment features, which consist of telescope like nested tubes, on the faces of which (on side of flow channel) are attached radially and axially or conically directed wall elements, which serve as separations from the adjacent suction chambers, and the circular face areas themselves, which serve in part as side walls of the flow channel or carry the corresponding ejector ring.
The components, previously mentioned and claimed, as described in the construction examples, to be used for the invention, are not subject to any special exceptions as to their size, shape, material selection and technical design, in which case the selection criteria, which is customary for the appropriate application, can be employed without limitation.